HIGHLY RELIABLE, HIGH-C DRAM STORAGE CAPACITORS WITH CVD TA2O5 FILMS ON RUGGED POLYSILICON

This paper reports on a highly reliable stacked storage capacitor with ultrahigh capacitance using rapid-thermal-annealed LPCVD-Ta2O5 films (approximately 100 angstrom) deposited on NH3-nitrided rugged poly-Si electrodes. The capacitances as high as 20.4 fF/mum2 (corresponding to the thinnest t(ox,eff) of 16.9 angstrom ever reported using LPCVD-Ta2 O5 and poly-Si technologies) have been achieved with excellent leakage current and TDDB characteristics. Extensive electrical characterizati on over wide temperature range (approximately 25-300-degrees-C) shows that the Ta2O5 films on rugged poly-Si electrodes have a better temper ature stability in dielectric leakage and breakdown compared to the fi lms on smooth poly-Si electrodes.